JP2500826Y2 - LCD projector - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention separates white light into three primary colors, modulates each with a liquid crystal display (LCD), and then synthesizes them again to project a full-color image. Liquid crystal projection device.

[Conventional technology]

Conventionally, the above-mentioned liquid crystal projection device is known as a device for displaying a television image, an output image of a personal computer, a word processor or the like on a liquid crystal panel and enlarging and projecting the same.

The principle of this type of device will be described with reference to FIG. 3. White light emitted from the light source 1 is reflected by the cold mirror M1 and, after passing through the UV filter F1 that cuts ultraviolet rays,
The red light R is reflected by the dichroic mirror DM1, the blue light B is reflected by the dichroic mirror DM2, and the green light G is transmitted through the mirror DM1.
Penetrates this. The red light R, the blue light B, and the green light G thus separated into the three primary colors are polarized by transmitting through the condenser lenses C1, C2, C3 and the liquid crystal panels 2, 3, 4 respectively arranged in each optical path. Modulation is applied. Then, the red light R and the blue light B are combined by the dichroic mirror DM3, and the green light G is further mixed by the dichroic mirror DM4.
Are combined, and the combined light passes through the projection lens 5 to project a full-color image on a screen (not shown).

As described above, since the color components of the three primary colors of red light R, blue light B, and green light G are projected by additive color mixing, in order to obtain a clear projected image without color shift, three sheets of It is necessary that each display pixel of the liquid crystal panels 2, 3 and 4 is projected at the same position on the screen, and that each projected image has the same size.

[Problems to be solved by the device]

However, if the respective optical path distances from the liquid crystal panels 2, 3, 4 to the projection lens 5 are made equal to each other, the light rays are refracted by passing through the dichroic mirrors DM3, DM4, so that the dichroic mirrors DM3, DM4 are respectively transmitted in the respective optical paths.
The front focus of the projection lens 5 differs depending on the presence / absence of transmission of light. Therefore, the size of the projected image on the screen is different for red light R, blue light B, and green light G,
There is a defect that the image becomes unclear. Therefore, in consideration of this, it is possible to adjust the distances between the projection lens 5 and the liquid crystal panels 2, 3 and 4 on each optical path by making them different from each other.
Then, this time, the incident angles of the red light R and the blue light B when passing through the same dichroic mirror DM4 (because the red light R is transmitted through the dichroic mirror DM3) are different in all directions. The projected image still has different sizes and shapes. Also, since the green light G does not pass through the dichroic mirrors DM3 and DM4, it does not have the same size as the other color lights, and eventually each liquid crystal panel 2, 3, 4 is projected on the screen as an image of a different size. There is a problem that the image becomes unclear.

This will be specifically described with reference to FIGS. 4 (A) and 4 (E).

On the paraxial line, when the dichroic mirror DM is not inserted in the optical path, as shown in FIG. 4 (A), the object point L (liquid crystal panel), the image point M on the screen, the principal point H of the projection lens 5,
If H ', the front focus is f + x and the back focus is f + x'. However, f is the focal length of the projection lens 5, x is the object point movement amount, and x'is the image point movement amount.

When the dichroic mirror DM is inserted as shown in FIG. 7B, the principal point H moves to the mirror DM side, so that the distance between the principal point H and the object point (liquid crystal panel) L becomes small. The distance l of the deviation is However, n: refractive index of the medium on both sides of the dichroic mirror DM (air; n = 1), n ': refractive index of the dichroic mirror DM, d: thickness of the dichroic mirror DM, and the imaging position of the object point L is Instead of moving on the screen, it moves to the rear (image point M of the broken line). Therefore, in order to form an image on the screen, it is sufficient to move the object point L backward by a predetermined distance as shown by the solid line and lengthen the front focus by l. In this case, depending on the presence or absence of the dichroic mirror DM, (f + x) and (f +
Since each value of x ') is the same, the magnification does not change.

Next, the marginal rays will be described. Assuming that the object point Y (liquid crystal panel) and the image point Y ′ are, when the dichroic mirror DM is not inserted as shown in FIG. An image point Y ′ is obtained on the screen by being incident and exiting at an exit angle θ according to Snell's law of refraction. When the dichroic mirror DM is inserted in the direction orthogonal to the optical axis as shown in FIG. 6D, the light enters under the same conditions as in FIG.
Similarly, if the position of the object point Y is moved from the position of the broken line to the position of the solid line, the peripheral light flux is superposed at the position where it exits the dichroic mirror DM, so the influence of the dichroic mirror DM disappears and the emission angle θ ′ = θ, The image point Y ″ is arranged on the screen, and its size is Y ″ = Y ′.

However, when the dichroic mirror DM is inserted and arranged at an angle of 45 degrees with respect to the optical axis in FIG. 6E, the optical axis O is displaced to the position of O ′, and the distance p on the screen is increased.
Deviation occurs. Therefore, when the position of the object point Y is shifted to the solid line position as in the case of (B) and (D) in the figure, the incident angle of the peripheral ray on the dichroic mirror DM is different by 2α ° between the upper and lower sides, and the output angle is different. Image point Y on the screen
Becomes larger than the image point Y ′ shown in FIG.

As is clear from the above description, a clear projection image cannot be obtained only by changing the distance between the projection lens 5 and the liquid crystal panels 2, 3, 4.

The present invention has been made in view of the above problems, and an object thereof is to provide a liquid crystal projection device having a simple structure, in which the sizes of the projected images of the respective liquid crystal displays are matched so that a clear image can be obtained.

[Means and Actions for Solving the Problems]

The liquid crystal projection device according to the present invention separates the white light from the light source into color lights of three primary colors by the separating dichroic mirror, modulates the color light of each optical path by transmitting through the liquid crystal display, and synthesizes by the combining dichroic mirror. , In a liquid crystal projection device configured to perform magnified projection through a projection lens, among the color light optical paths between the liquid crystal display and the projection lens, the combination dichroic mirror that has the most light paths for the combination dichroic mirror through which color light passes is In order to match the total wall thickness and the glass wall thickness including the dichroic mirror for synthesis that transmits the color light of the other optical paths, the transparent glass of the predetermined wall thickness is arranged in each of the other two color light optical paths. It is a thing.

Therefore, each color light separated into three colors by the separating dichroic mirror is transmitted through the liquid crystal display device and modulated,
The light is transmitted through the dichroic mirror for synthesis having the same glass thickness or the transparent glass, or both, and is synthesized, and is projected as a clear projected image having the same image size on the screen through the projection lens.

〔Example〕

A preferred embodiment of the present invention will be described below with reference to FIGS. 1 and 2, but the same parts as those of the above-described conventional art are designated by the same reference numerals and the description thereof will be omitted.

In Fig. 1, each dichroic mirror DM1, DM2, DM
3, DM4 and the mirrors M1, M2, M3 are respectively arranged on the optical path at an angle of 45 ° with respect to the optical axis O. In the figure, 7 is a transparent glass arranged at the same angle as the dichroic mirror DM4 between the liquid crystal panel 3 and the dichroic mirror DM3 on the optical path of the blue light B. The thickness of the transparent glass 7 is the same on the same optical path. DM4 placed dichroic mirror
The total thickness of the two is the DM of the optical path of the red light R, which is equipped with the most dichroic mirrors DM3 and DM4 that transmit color light.
It is set to match the total thickness of 3 and DM4 (see FIGS. 2 (A) and 2 (B)). Reference numeral 8 is a transparent glass arranged on the optical path of the green light G between the liquid crystal panel 4 and the dichroic mirror DM4 at the same angle as the mirror DM4. The thickness of the transparent glass 8 is on the optical path of the red light R. It is set to be the same as the total thickness of the dichroic mirrors DM3 and DM4 (see FIGS. 2A and 2C).

Since the present embodiment is configured as described above, among the white light emitted from the light source, the dichroic mirror DM1
The red light R reflected and split by the mirror M2 is reflected by the mirror M2, transmitted through the liquid crystal panel 2 and modulated, and then transmitted through the dichroic mirrors DM3 and DM4 to reach the projection lens 5.
The blue light B reflected and divided by the dichroic mirror DM2 is transmitted through the liquid crystal panel 3, modulated, and then transmitted through the transparent glass 7, reflected by the dichroic mirror DM3, and further transmitted through the dichroic mirror DM4. To reach the projection lens 5. In this case, since the blue light B is transmitted through the glass member having the same thickness as the red light R at the same angle, the two images projected on the screen via the projection lens 5 have different sizes and display pixels. The positions of are exactly the same.

Further, the divided green light G transmitted through the dichroic mirror DM2 is transmitted through the liquid crystal panel 4, modulated, and then reflected by the mirror M3 and transmitted through the transparent glass 8, reflected by the dichroic mirror DM4 and projected by the projection lens. Reach 5. In this case, since the green light G is transmitted through the glass member having the same thickness as the red light R and the blue light B at the same angle, the three images projected on the screen via the projection lens 5 have different sizes. And the positions of the respective display pixels completely match.

As described above, according to the present embodiment, with a relatively simple configuration, the color-separated color lights R, B, and G can be combined and projected on the screen as a completely identical image. A clear projection image can be obtained. Further, when separating the light beams of the three primary colors, the light beams are not necessarily limited to the order shown above, and the light beams of any color may be separated.

Incidentally, in the above-mentioned embodiment, the transparent glass is 45 with respect to the optical axis.
Although they are arranged at an angle of °, they may be arranged at an appropriate different angle. In this case, it is not a perfect match, but a considerable effect is obtained.

Further, a single transparent glass 8 is arranged in the optical path of the green light G, but a plurality of transparent glasses may be used as long as the total thickness is the same, and the same applies to the transparent glass 7.

The dichroic mirrors DM1 and DM2 form a separating dichroic mirror, and the dichroic mirrors DM3 and DM4 form a combining dichroic mirror.

[Effect of device]

As described above, the liquid crystal projection device according to the present invention has the same glass wall thickness on the light path of each color between the liquid crystal display and the projection lens, including the dichroic mirror for synthesis through which each color light passes. Since the transparent glass having a predetermined thickness is arranged on the two optical paths, the projected images can be perfectly matched on the screen, and an extremely clear projected image can be obtained. Moreover, the structure is simple and the increase in manufacturing cost can be suppressed.

[Brief description of drawings]

FIG. 1 is an optical path diagram of a liquid crystal projection device showing an embodiment of the liquid crystal projection device according to the present invention, and FIG. 2 is an optical path diagram of each color light. (A) is red light R, (B) is Blue light B,
(C) is a green light G, FIG. 3 is an optical path diagram of a conventional device, and FIGS. 4 (A) to (E) are diagrams illustrating an optical path of the conventional device. 1 …… Light source, DM1, DM2, DM3, DM4 …… Dichroic mirror, 2,3,4 …… Liquid crystal panel, 5 …… Projection lens, 7,8 ……
Transparent glass.

Claims (1)

(57) [Scope of utility model registration request] 1. White light from a light source is separated into color lights of three primary colors by a separation dichroic mirror, and the color lights of respective optical paths are modulated by passing through respective liquid crystal displays, and then combined by a combining dichroic mirror, In a liquid crystal projection device for enlarging and projecting through a projection lens, among the respective color light optical paths between the liquid crystal display and the projection lens, the combination dichroic mirror having the largest number of the combination dichroic mirrors through which color light passes In order to match the total thickness of the glass and the glass thickness including the dichroic mirror for synthesis that transmits the color light of the other optical paths, the glass with the predetermined thickness is arranged in each of the other two color optical paths. A liquid crystal projection device characterized in that